When you’re using Windows you must set the WDM drivers to render to four speakers, if not (and mostly it is not set by default) you’ll get the effect you’re talking about. AFAIK FMOD uses DirectX and DX supports the four speakers in software mode I think, but I’m not sure.

So, when we load in software buffers, there’s not 4 speakers support, but just an stereo emulation of 3D positioning.
But if we load in hardware buffers, it sounds fully 3D, using the 4 speakers if set DX to use them, no?